1. Field of the Invention
The present invention relates to a semiconductor device having contact holes formed on a semiconductor substrate and a method of fabricating the same.
2. Description of the Related Art
For example, JP-2000-150637A discloses a technique of forming contact holes on a source/drain region of a semiconductor substrate. In this technique, first and second silicon oxide films are stacked into a two-layer structure on the semiconductor substrate as an interlayer insulating film. Each contact hole includes a vertical side wall extending through a second silicon oxide film and a tapered face extending through a first silicon oxide film. A metal wiring layer is connected to the source/drain region via the contact holes provided in the interlayer insulating film.
A diameter of the contact hole has recently been reduced with recent reduction in design rules and element refinement. Accordingly, this results in an increase in the aspect ratio and consequently, since an aspect ratio is increased, a filling property is reduced when the contact hole is filled with a metal wiring layer. When the filling property is low, seams occur in the metal wiring layer, which results in an increase in a resistance value of the metal wiring layer.